// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_MEMORY_MEMORY_PRESSURE_MONITOR_H_
#define BASE_MEMORY_MEMORY_PRESSURE_MONITOR_H_

#include "base/base_export.h"
#include "base/macros.h"
#include "base/memory/memory_pressure_listener.h"

namespace base {

// TODO(chrisha): Make this a concrete class with per-OS implementations rather
// than an abstract base class.

// Declares the interface for a MemoryPressureMonitor. There are multiple
// OS specific implementations of this class. An instance of the memory
// pressure observer is created at the process level, tracks memory usage, and
// pushes memory state change notifications to the static function
// base::MemoryPressureListener::NotifyMemoryPressure. This is turn notifies
// all MemoryPressureListener instances via a callback.
class BASE_EXPORT MemoryPressureMonitor {
public:
    using MemoryPressureLevel = base::MemoryPressureListener::MemoryPressureLevel;

    virtual ~MemoryPressureMonitor();

    // Return the singleton MemoryPressureMonitor.
    static MemoryPressureMonitor* Get();

    // Returns the currently observed memory pressure.
    virtual MemoryPressureLevel GetCurrentPressureLevel() const = 0;

protected:
    MemoryPressureMonitor();

private:
    DISALLOW_COPY_AND_ASSIGN(MemoryPressureMonitor);
};

} // namespace base

#endif // BASE_MEMORY_MEMORY_PRESSURE_MONITOR_H_
